Firearms officers were "put on the spot" when they were controversially handed unauthorised shotgun Tasers in a doomed bid to bring in Raoul Moat alive, a police weapons expert said.

X12 shotguns had never been used in a UK operation before and were only licensed for testing purposes. When they were deployed in Rothbury, Northumberland, it was the first time officers had handled them.

Peter Boatman, an ex-police firearms officer and director of UK suppliers Pro-Tect Systems, offered them to Northumbria Police in the belief the non-lethal weapons would make officers on the manhunt safer.

The X12, which fires XREP cartridges over much a longer range than conventional hand-held Tasers, were developed to fill a gap in law enforcers' armoury by locking up suspects' muscles from distance.

Conventional X26 Tasers work best at up to three metres, while X12s have a range of 10 times that.

But on the night, the XREP which hit Moat failed to deliver neuro-muscular incapacitation and the cornered killer escaped justice by putting a shot through his own head.

Andy Redhead, a retired police national tactical firearms adviser who worked with the Metropolitan and Northumbria Police forces, said: "The guys were put on the spot on the night.

"Tasers are still relatively new to us in the UK and the shotgun Taser was totally new."

Mr Redhead, now a director of the security firm Sec-Tech, sympathised with Assistant Chief Constable Steve Ashman's decision to go against Association of Chief Police Officers guidelines which ban the use of unauthorised weapons.

Mr Ashman has told the inquest he believed Moat's right to life under the Human Rights Act meant police should do all they could to bring him in alive, and that meant using an XREP to incapacitate and arrest him.

Mr Redhead said: "It was a unique set of circumstances - I understand ACC Ashman's comments and sympathise with them."

At the inquest a Home Office expert said the shotgun Taser technology was ineffective, and the jury heard that the XREP cartridge did not pierce Moat's skin, but got caught up in his sodden hoodie. Moat also failed to grasp the cartridge's trailing wires which are designed to make the subject grab them, creating a secondary contact for the electrical discharge to pass through.

But Taser insist their product works, and claim the Home Office assessment was based on old data and that the XREP has been much improved since then.

Steve Tuttle, Taser's vice president of communications, said: "It's not a perfect weapon, there are no magic bullets."

But the XREP technology has been sold to 32 countries and he has many examples of its successful use, he said.

Mr Tuttle said: "Our products cannot be something that works one in 20 times. We have had numerous uses where it has been successful.

"The Home Office looked at a study that's quite old and we refute it."